The purpose of this study was to examine the effect of science instruction given through the game and physical activities course in accordance with interdisciplinary teaching approaches on students' science achievement and retention. The participants were 82 third grade students from a public elementary school. Three classes were chosen as experimental groups and one class was chosen as a control group in the school. The instruction period lasted for five weeks in all groups. The data were collected by an achievement test and an education portal achievement (EPA) test. The pretest-posttest control group design was used in the study. Data obtained from the tests were analyzed through one-way analysis of variance and post-hoc analyses. The findings indicated that some of the experimental groups were more successful than the control group with large effect sizes. The results suggested that the game and physical activities course incorporating interdisciplinary teaching approaches could be used in increasing students' science achievement and retention of science knowledge.